Smartphones Aren’t Giving You Cancer

Why you don’t need to worry about your phone killing you

Gideon M-K; Health Nerd
6 min readMay 1, 2018
Pictured: The root of all evil (probably)

Smartphones are one of the most amazing advances in the history of arguments. Prior to the noughties, if you wanted to check if something was true to prove your family wrong at dinner, you had to dig out the encyclopedia or find an actual expert.

No more. Now it takes less than a few seconds to prove that bananas are all clones of each other.

Pictured: Clones. Yes, clones. It’s super cool

Of course, there are other benefits to smartphones. They allow us to communicate, they network the world in new and innovative ways, and let’s not forget the wonderment of selfies.

Truly, an amazing invention

And because of these amazing aspects, smartphones have become truly ubiquitous. You can find one in the hand of nearly half of all people worldwide. Which makes it even more scary when stories are published in the news telling us all that our smartphone isn’t actually our friend.

According to the media, your smartphone might be killing you.

Here’s why they’re wrong.

Cancerous Nonsense

The usual premise behind the smartphone/cancer link goes something like this:

“Smartphones are giving off electromagnetic radiation. That has the word radiation in it, and we all know radiation causes cancer!”

This is, of course, stupid. Electromagnetic radiation includes things like light, heat, and radio. If all electromagnetic radiation gave us cancer, there’d probably be quite a bit more cancer.

The Sun is basically just a huge ball of flaming radiation — it’s also responsible for all life on earth

But now there’s a new scary story about smartphones out. According to many news stories, the light that smartphones give off — as well as some other things in our environment, including most streetlights — may be killing us just as surely as carrying around an enormous lump of radium.

These stories are also, sadly, wildly incorrect.

Pictured: Wrong

So what’s happening here?

The Science

The researchers in this story did something really interesting. They took pictures of two Spanish cities at night — Barcelona and Madrid — and mapped out visible light based on a clever algorithm. They then asked a large sample of people in these areas and others how much light they were exposed to in their bedroom, and finally compared how much these two factors — indoor and outdoor night light — were linked to breast and prostate cancer.

They found that there was a statistically significant correlation between a specific type of outdoor light and cancer, as well as a connection between prostate cancer and sleeping in a bedroom with high levels of light.

And from this, the terrifying headlines.

Pictured: Eeeeevvviiiillllll

So does this mean we should throw away our smartphones forever and move to the caves where it’s nice and dark?

Not in the slightest.

Ridiculous Conclusions

This study was, essentially, wildly speculative. The connections that the scientists drew were extremely vague — how do you relate outdoor light to the amount of light someone is actually exposed to? As the study mentions, outdoor light is “ubiquitious”, so it seems odd that higher levels would be related to cancer — the background rate is so high already, an increase is probably not going to do much.

It’s also extremely difficult to look at pictures from 2012 and 13 that were taken from space, and relate them to the actual amount of light on the ground. And when I say extremely difficult, I mean basically impossible.

Pictured: Not easy to draw conclusions from

Or, to quote the authors in the study itself:

“In other words, the light output pattern of the light fixtures cannot be assessed from space, and it is possible that the upward light remains weakly correlated to the horizontal light that enters the houses.”

Essentially, this means that it’s really hard to say that the amount of light that was measured in the space pictures has any reflection on the light that people actually experience.

Even worse than all of this was that this study was very observational. Drawing conclusions from observational research is tough, because ultimately you can only control for so many factors. For example, in this study there was no correction for type of work that people were doing — some jobs may be associated with much higher light exposures in the bedroom than others. It’s entirely possible that the observed correlations between cancer and light were just down to statistical chance.

Speaking of statistics, they were…not ideal.

Statistical tests are similar to flipping a coin. Do enough of them, and you’ll see at least one heads. In this study, the authors did about 20 statistical tests, and found 3 positive correlations, without doing what’s known as “controlling for multiple comparisons”. What this means is that there’s a good chance that even the ‘significant’ results actually aren’t.

From the study. The ‘significant’ results are boxed in red

There are other issues with the statistics — splitting continuous variables into tertiles and testing lowest vs highest is a bit odd, as you’d usually use regression to measure the association, and while these results were technically significant, they are so close to insignificant that it is a bit of a stretch to say the research found anything at all — but basically the point is that these results are extremely preliminary and not to be taken out of context.

Which is what the scientists said.

Media Madness

The thing about this study is that it was a very preliminary test of a hypothesis. Mostly, what the scientists were trying to do was see if the idea that blue light was bad for you could be seen in a population study.

Pictured: Science-speak for “We aren’t sure if this means anything at all”

Which anyone who actually read the study would easily have realized. They say it right there in slightly science-y language.

It’s the same old science reporting story: study gets published, press release comes out, no one reads the actual research, and suddenly everyone’s terrified of smartphones despite there being no evidence that they cause cancer at all.

Seriously, the authors don’t even specifically mention smartphones once.

One point that reinforces this is that if phones (or blue light, or even light generally) caused breast or prostate cancer, you’d expect rates to be skyrocketing as sales did. But what you actually see are very minor increases that are mostly related to the population aging: there’s no evidence whatsoever of a massive increase in cancer due to smartphones or light generally.

Might there potentially, possibly be some influence of light on our health? Of course. Is there enough evidence to worry even the slightest bit about your smartphone use? No. Definitely not.

Don’t believe the scary stories.

There’s no reason to believe that smartphones are giving you cancer.

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Fun bonus for anyone reading my italics — it turns out that there aren’t even really pictures of old phones these days. All the stock photos when you search “phone” come up with smartphones, mostly iPhones, which is either a sad indictment of society or cultural progress depending on when you were born and how much a fan of retro things you are.